Stocking Charts for Selected Tree Species and Forest Types
Stocking charts are useful thinning guides. If you know the square feet of basal area and number of trees per acre in a stand, you can refer to a stocking chart for the species of interest and determine whether the stand is overstocked, fully stocked, or understocked. Stands above the A level on a stocking chart are overstocked and should be thinned back to near the B level to increase tree growth rate.
For example, refer to Appendix C-2. If your stand had a basal area of 110 square feet and 200 trees per acre, it would be at the A level where it is nearly overstocked. Trees in the stand would grow faster if the stand were thinned. Trees in this sample stand have an average stand diameter of 10 inches. Follow the line for 10 inches diameter down to the B-level curve. It intersects the B-level curve where the basal area is 68 square feet and there are 125 trees per acre. The residual trees would grow best if the stand were thinned back to this stocking level.
However, a stand that is heavily thinned may be subject to windthrow and epicormic branching. As a rule of thumb, do not remove more than one-third of the basal area from a stand at any one time. Applying this principle to the example above, the stand should be thinned down to 74 square feet of basal area and approximately 135 trees per acre.
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